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8. Installation Sites For SkyWind NG
Seite 22
| Owners Manual SkyWind NG, Version 5.1
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8.3 Annual Yield
Some of the major requirements for successful operation of your wind turbine have already
been described on the last pages. Besides a correct installation and a non turbulent site the
main ingredient for a well working turbine is obviously the available wind power itself. To pre-
dict the success of your project you need to check your sites average annual wind speed. This
can be done by typing your address at
www.globalwindatlas.info
and choosing a height of 10
m above ground level.
Often an
(incorrect!)
rule of thumb is told on how to calculate wind speed:
Hours per year (8760) x Power at 5 m/s (0,04 kW) = 350 kWh/Year |
WRONG
This calculation does not take into account, that the wind speed will often be more than 5 m/s
as this is only the statistic average. But the energy generated per time will increase massively
with higher wind speeds. A simple calculation can illustrate that:
10 h x Power at 5 m/s (0,04 kW) = 0,400 kWh
5 h x Power at 10 m/s (0,275 kW) = 1,375 kWh
Twice the wind speed for half as much time will generate almost four times as much energy!
For this reason a site with 5 m/s could actually expect about 750 kWh per year instead of the
350 kWh calculated with the (incorrect) rule of thumb.
To predict how much energy your turbine will generate a computer calculated yield curve for
the exact wind turbine type has to be used. This curve must take into account the specific
performance of the exact wind turbine type at different wind speeds. For the SkyWind NG
you can find this graph on the right.
Only with computer programs and detailed power curves
of the wind turbine a reliable prediction of the actual yield becomes possible. Still, this yield
may vary by up to +/
-
50% per year (depending on the site) due to seasonal effects and one
year beeing more windy than the other. However, if wind and solar are used together this
effect is almost neutralised as a year with less wind will usually provide more sun energy
-
and
the other way around.
Never use rule of thumb or
„
full hour
“
calculations to estimate your
turbines yield.
Even the best calculation can only be accurate when the site is free of
turbulence and the turbine is installed correctly.
Yield estimates are always based on long time annual averages. The
actual yield may vary depending on the real situation in that year.
Power production calculated for k=1.8,
Air density of 1,293kg/m³, Production may vary due to turbulence and air density.
